Large sheet material is awkward to handle, especially when the material is thin and is of a large lateral and linear dimension. The large sheet material, besides being clumsy, is heavy and hard to hold while at the same time it is extremely vulnerable to being creased or permanently bent. Furthermore, such material is susceptible to surface marring by virtue of handling apparatus. Therefore, it is desirable to maintain such material in stacked configurations such that only the upper and lower sheet are susceptible to surface marring. Accordingly, it has been known in the past to utilize material handling apparatus which unstacks sheets of the panel-like material, processes the material and restacks the sheets. It should be noted, however, that the prior art has failed to deal with the problem of sheet material of varying resiliency. That is to say, a sheet of material depending upon the type of material, has a certain resistance to bending transversely of its longitudinal axis. This resistance to bending varies depending upon the thickness of the material and the type of material, accordingly, apparatus which have heretofore to unstack such material have been designed with a particular resiliency in mind. Again, that is to say, the apparatus has been designed with limitations dictated by the type of material being handled.
In addition to the limitations of the prior art imposed at the unstacking station, the utilization of automated machinery to position large sheets of material for operations thereon by materials such as turret presses has been less than satisfactory. One problem associated with the prior art devices is the ability to accurately and repetitively align the machinery with the turret press such that the press may utilize the maximum area of the sheet for its operations. Yet another problem associated with such operations is the removal of processed sheets from the rotary press in a manner which will allow the sheets to be stacked in an orderly fashion. As is well known, normally such sheets have portions thereof removed proximal the leading and trailing margins, therefore it is difficult for grasping apparatus to securely grip the material and to propel the material along in an aligned condition.
One a sheet of material has been properly punched, it is then also imperative that it be expeditiously removed from the punch area into a reformed stack. Prior apparatus have been successful in restacking material, however their rate of operation leaves something to be desired. One limitation seen in the prior art is the utilization of a disappearing roller table to support a sheet member instantaneously during the stacking operation. In the prior art such disappearing tables usually are movable in the direction of travel of the sheet member therefore the table must move to one end of the sheet to allow a sheet to descend and then reposition itself before a new sheet may be supported thereon. While such an arrangement is acceptable when a plurality of sheets are to be stacked atop the disappearing table, when each sheet must be individually handled by the disappearing table, it is clear that the time required for this type operation is excessive.